This application claims priority from Federal Republic of Germany Patent Application No. 102 10 141.8 filed on Mar. 7, 2002.
The invention relates to a car body part for a motor vehicle, in particular a roof module, as well as to a method of producing such a car body part.
Vehicle bodies are constructed by attaching car body parts together. As an example, a roof railing may be attached to a roof module or a second car body part. Typically, the prior art has provided either additional fastening elements or other particular provisions for connecting the two car body parts. Usually, holes are formed in the car body part. This has disadvantages both in terms of assembly time and expense. Also, with such connections, tolerances have to be kept small so that undesirably large gaps will not occur between the car body parts.
It is an object of this invention to provide a car body part which can be fastened to other car body parts inexpensively and which provides visually appealing small gaps.
According to the invention, a car body part for a motor vehicle has an outer skin formed from an at least partially deformable material, and an inner layer formed of a foamed plastic. A mounting part is placed in a recess of the outer skin and is anchored there by an interlocking fit. A main feature of the invention is the basic idea of clamping the mounting part in the recess of the outer skin. To this end, the invention may use an elastic pretension of the car body part. A force holding the mounting part in the recess is increased, by providing anchoring protrusions on the mounting part. The anchoring provisions are forced into the outer skin of the car body part. By positioning the mounting part in the recess, low dimensional tolerances are achieved.
To clamp the outer skin against the mounting part, it is particularly suitable to use the inner layer. The inner layer is formed of a foamed plastic. The inner layer may also be provided with reinforcement fibers, for instance glass fibers. The formed inner layer has the particular advantage that a foaming pressure generated during foaming of the inner layer, can be used to strongly press the outer skin against the mounting part and deform the outer skin in the process. In this way, the mounting part is received with an interlocking fit.
It is particularly suitable to use a rail as the mounting part. The rail can be, for instance, an extruded aluminum profile with a plurality of anchoring protrusions on an outer surface. As mentioned above, the anchoring protrusions provide a positive anchoring of the mounting part in the outer skin. It is also possible to use a mounting part in the form of e.g. a threaded piece, which may serve as a base part of a roof antenna, for instance.
It is also particularly suitable to use a second car body part having a bent-off edge portion which is accommodated in the recess of the first car body part. This provides assemblies which on the one hand are preferably formed from deep-drawn plastic parts, while still having dimensions or shapes which could not be obtained if formed in one piece.
Preferably the recess in the outer skin has a rectangular cross-section and the mounting part is fully received in the recess. This makes it possible to fasten a mount-on part, such as a roof railing, to the mounting part, if required. On the other hand, if no mount-on part is used, a covering may be attached which is flush with the outer surface of the outer skin to ensure an acceptable visual appearance.
The mounting part may also be designed to terminate flush with the outer surface of the outer skin and match the curvature of the outer skin. In this way, a visually uninterrupted outer contour is achieved.
The desired deformability of the outer skin is provided if the outer skin is made of plastic. While the outer skin is deformable, the inner layer provides the required strength.
When plastic is used for the outer skin, then the recess in the outer skin can also be provided with an undercut. The mounting part may latch in place automatically behind the undercut. Once the inner layer is formed, the force holding the mounting part in the outer skin is further improved. An undercut will not raise problems removing the outer skin from a mold, because the yielding nature of the plastics material is sufficiently high.
A car body part according to the invention can be a roof module. In this case the mounting part may be one which allows the simple attachment of the various mount-on parts typically provided on a roof module.
The invention also provides a method of producing a car body part and, in particular, a roof module. In this method, an outer skin having a recess is formed. A mounting part is then placed in the recess. The outer skin, including the mounting part, is placed in a foaming mold. A foamed inner layer is applied on the rear side of the outer skin. A foaming pressure generated in this process strongly presses the outer skin against the mounting part. In this way, the mounting part is firmly anchored in the recess. This method thus makes use of the existing foaming pressure, for fastening the mounting part to the outer skin. Hence, additional process steps are not required which results in reduced process costs.
The outer skin can be deep-drawn, in particular, to form the recess for receiving the mounting part. In this way the recess can be produced in a very cost-effective manner. In fact, the recess can be formed in one single step during formation of the outer skin.